1. Field of the Invention
The present invention relates to a power amplification apparatus which are suitable for application to a mobile telephone, a PHS phone (Personal Handy-phone System), a PDA apparatus (Personal Digital Assistant) provided with a communication function, and a terminal apparatus such as a note-type personal computer using a communication function, and a mobile communication terminal apparatus.
2. Description of Related Art
Now, in Japan, the number of subscribers using mobile phones has exceeded 70% of the population, and approximately 40% of them are owners of mobile communication terminal apparatus which uses a CDMA (Code Division Multiple Access) technology. In the future, when the demand for these terminals is replaced from PDC (Personal Digital Cellular) terminal apparatus and the like by a mobile communication terminal system based on a W-CDMA (Wideband-CDMA) method, the demand for the mobile communication terminal system is anticipated to grow further.
In a mobile radio communication system using the PDC, CDMA methods or the like, such communication is secured between a mobile terminal and a base station by establishing a radio channel there-between. However, because of a changing communication distance from the base station or due to fading in a transmission path, a signal level will change from time to time. Therefore, in a transmission system of the mobile terminal, it is arranged such that after adjusting a transmission signal to a desired signal level in a power amplifier, the signal is transmitted to the base station.
Conventionally, it has been attempted to improve an efficiency of its operation by use of a DC-DC converter in a power supply of the power amplifier in the transmission system. However, because the DC-DC converter generates a noise, and in addition, large capacity coils are required, there are many problems still to be solved.
On this account, a patent document 1 (Japanese Laid-Open Patent H9-130275) discloses again adjusting method for a transmission signal to achieve an improvement of an operation efficiency in a power amplification apparatus while suppressing unnecessary power consumption by selecting a signal path including signal amplification means having a gain corresponding to a desired signal level among a plurality of signal paths each including signal amplification means having a different gain, by amplifying and outputting the transmission signal with the gain of the signal amplification means of selected signal path, and by stop-controlling the operation of the signal amplification means of non-selected signal paths.
Patent Document 1 (Japanese Laid-Open Patent H9-130275)
However, a recent mobile phone is added with many functions of a so-called application such as a present location detection function with a GPS (Global Positioning System) sensor, a TV signal receiving function, an infrared communication function, a TV telephone function with a camera and the like. Therefore, an occasion of performing a high speed communication with the base station is increasing, and also a period of time for performing this high speed communication is prolonging. Thereby, an average transmission power is increasing to more than 10 mW, and thus it is required more and more to enable to deliver a transmission power which is amplified to a large power without causing any loss.
Further, in case of the technology disclosed in the patent document 1, it is configured to use by switching a plurality of signal amplification means connected in parallel, so that a circuit scale becomes larger, and it tends to be a multi-chip form in case of implementing the circuit.
There has been a strong demand for further miniaturization in the recent mobile communication terminal system, and it is necessary to form the power amplification apparatus in an one-chip form, even for satisfying such demand.
The present invention has been contemplated in consideration of the above-mentioned problems, and is configured to provide a power amplification apparatus and a mobile communication terminal apparatus which are capable of remarkably improving the operation efficiency, and further of integrating to be one-chip form.